ah – Git Hooks¶

Escript that is installed as a universal git hook in all managed repositories. On every hook invocation, ah connects to the local Frontend Connector (af) which forwards the request to the Manager (am).

How It Works¶

sequenceDiagram
    participant Git
    participant ah as ah (escript)
    participant af as af (Frontend)
    participant am as am (Manager)

    Git->>ah: hook triggered (e.g. pre-receive)
    ah->>ah: start Erlang node (ah_<pid>)
    ah->>af: gen_server:call({global, af_hook_server}, {git_hook, ...})
    af->>am: gen_server:call({global, am_hook_api}, {git_hook, ...})
    am->>am: start am_hook_handler
    am-->>af: result (allow / deny)
    af-->>ah: result
    ah-->>Git: exit code 0 or 1

Git triggers a hook (e.g. pre-receive, update, post-update)
ah starts as an escript with a unique node name (ah_<PID>@<host>)
Connects to the local af node via net_adm:ping
Calls gen_server:call({global, af_hook_server}, {git_hook, HookData})
af forwards the request to the Manager (am) and returns the result — ah passes it back to git

Data Sent to af¶

Field	Description
`hook`	Name of the hook (e.g. `"hooks/pre-receive"`)
`args`	Hook arguments (branch name, old/new hash)
`stdin`	Data read from stdin (ref data for pre-receive etc.)
`env`	Filtered environment variables (`GIT_*`, `PWD`)
`cwd`	Current working directory (path to the repository)

Installation¶

ah is linked or copied as all hook files into the hooks/ directory of each bare repository. Since ah determines the hook name from escript:script_name(), a single binary works for all hook types.

cd /path/to/repo.git/hooks
for hook in pre-receive update post-update post-receive; do
    ln -sf /home/git/ah $hook
done

Build¶

cd applikant.git-in/ah
rebar3 escriptize
cp _build/default/bin/ah /home/git/ah

Configuration¶

Environment Variable	Default	Description
`APPLIKANT_COOKIE`	`applikant_cookie`	Erlang distribution cookie
`APPLIKANT_AF_NODE`	`af@localhost`	Erlang node name of the local `af` instance

Status¶

Work in progress

Basic hook communication via af to the Manager works. Real permission logic in the Manager is not yet implemented.